1. Field of the Invention
This invention relates to an electrode system for measuring ions and dissolved gases in a solution.
2. Description of the Prior Art
Concentrations of ions and dissolved gases in various industrial waters, including suspensions and solutions in the process of chemical reaction as well, have already been measured and monitored. In clinical fields, too, it has recently become common practice that gases and electrolyte concentrations in blood are measured in order to check the condition of diseases and carry out bedside diagnosis. For example, the analysis of electrolyte in blood is indispensable for diabetics and patients suffering from kidney trouble. In the case of an immature infant requiring respiratory control, excessive oxygen in the blood results in retinitis, and conversely a shortage of oxygen sometimes brings about death or cerebral palsy. Vesicular emphysema and bronchial asthma at times give rise to increase in pCO.sub.2 (partial pressure of CO.sub.2) in arterial blood and heart failure sometimes results in decrease in pCO.sub.2. Sooner or later, importance will be placed in the continuous analysis of arterial blood, especially during an operation. After an operation, too, blood gas analysis is indispensable for checking the condition of a patient who undergoes the operation.
U.S. Pat. No. 2,913,386 discloses an electrolytic device for use in chemical analysis, particularly in a polarographic cell adaptable for use in making quantitative analyses, especially continuous analyses. It covers an electrode pair supported in predetermined spaced relationship and electrically connected by an electrolyte and a selectively permeable barrier for separating the electrode pair and the electrolyte from the composition to be analyzed.
U.S. Pat. No. 3,505,195 discloses an electrode system for electro-chemical measurements of a liquid sample of the type employing at least two electrodes comprising an indicator electrode and a reference electrode. The indicator electrode is vertically disposed in the system and the top surface of the indicator electrode comprises a membrane which defines the bottom wall of the measuring chamber in which the sample is freely accessible from above.
U.S. Pat. No. 3,763,422 discloses a system for determining values of pH, pCO.sub.2, and pO.sub.2 in a small sample of blood. The system comprises a measuring chamber common to the sensing portions of a flow-through pH electrode, a pH reference electrode, a carbon dioxide (pCO.sub.2) electrode, and an oxygen (pO.sub.2) electrode. In line and communicating with the chamber exit is a peristaltically activated pump which can drove small samples of blood into the chamber followed by a vacuum system for drawing the sample out of the chamber. Communicating with the chamber entrance is a flush system for cleansing the chamber after the blood has been analyzed.
U.S. Pat. No. 3,732,159 discloses a flow-through sample analyzing chamber in which the electrodes are symmetrically disposed with respect to the fluid inlet and outlet passages, and the chamber construction is such that the flow of fluid therein is symmetrical. A conductive screen may be disposed in the fluid path to provide a uniform electrical field in the vicinity of the active portions of all electrodes.
Concerning glass in use for ion selective electrodes, much work has been done by numerous investigators. Among them U.S. Pat. No. 2,444,845 discloses a glass composition for a pH sensing electrode.
Briefly, little attention has been paid to the structure of the electrode for analyzing fluid such as blood which easily coagulates on the sensing portion of an electrode. The coagulation of blood causes many disadvantages including the response of the electrode to the characteristics of the blood, a poor reproducibility of data, an unstable reading and a short performance life.